Better headings order across all pages

[alexstine]

Always keep the heading 1 Photos title that way users always know what site they are looking at on the wordpress.org network. Also changes other heading 1 to heading 2. Likely needs design.

[alexstine]

Keeps Photos site title as heading 1 for all pages. Change existing heading 1 to heading 2.

[coffee2code]

Related to #4110 (which is a general request to make this sort of improvement across all of w.org).

I tried this out and was pleasantly surprised to see that the changes required no design changes and everything continued to look the same. I had thought -- given that the site makes use of styles shared across w.org and that the general markup is largely taken from other sites -- that this might have required a more coordinated update with general .org design changes or a lot of local overrides. But no.

I'll test it out a bit more and land this soon.

[coffee2code]

In 11647:

Photo Directory: Improve headings.

Converts all but a singular header heading from h1 to h2. No design changes necessary.

Props alexstine.
Fixes #6141.